The LDG RT-100 is an automatic tuner intended for outdoor mounting at or near the antenna feedpoint, minimizing SWR losses in the transmission line. It handles up to 125 watts on SSB and CW. The RT-100 is weatherproof, and is powered over the coaxial cable via the included RC-100 remote controller/Bias-T.The RT-100 will automatically tune when the SWR exceeds a preset limit. You can also manually begin a tuning cycle or bypass the tuner from the RT-100 remote. DC power for the tuner is applied to the RT-100 near the operating position and transferred to the tuner over the coax.Like all LDG tuners the RT-100 operates automatically, beginning a tuning cycle whenever the SWR exceeds a preset limit. It also features LDG's advanced memory tuning, providing 2,000 memory locations; when tuning near a previously used frequency it will recall the settings for nearly instant tuning. It learns your favorite frequencies and bands as you use it. You can also start a tuning cycle manually whenever necessary.All LDG tuners come with a two year fully transferable warranty. For ATAS mode operation with Yaesu FT-891, 991(A), 857(D), 897(D), 450(D), 100(D) radios: 1] place radio ATAS mode 2] Press PTT and press “Up” on mic. 3] Tuner will tuner with 10 watts. 4] Operate normally. Optional external Balun allows tuning of random length, long wire or ladder line fed antennas.